Copy classes to slide div

This allows you to style the slide itself, instead of just the content.
This means that you can apply edge to edge images, for example.
css cleanups

Align the supplemental sections when printed.
Also, bump up presenter notes so they're readable!
Merge pull request #72 from binford2k/css_cleanups

css cleanups
Merge pull request #73 from binford2k/features/copy_content_class_to_slide_div

Copy classes to slide div